Device for producing cold and/or liquefying gases



Feb. 18, 1969 J. A. RIETDIJK 3,427,317

DEVICE FOR PRODUCING COLD AND/OR FOR LIQUEFYING GASES Filed Dec. 2, 1965Sheet of 5 INVENTOR. JOHAN A. RIETD/JK Feb. 18, 1969 J. A. RIETDIJKDEVICE FOR PRODUCING COLD AND/OR FOR LIQUEFYING GASES Sheet FIG.2

: INVENTOR. JOHAN A. RIETDIJK AGEN Feb. 18, 1969 J. A. RIETDIJK3,427,817

DEVICE FOR PRODUCING COL-D AND/OR FOR LIQUEFYING GASES Filed D80. 2,1965 Sheet 3 0f 5 INVENTOR. JOHAN A. RIETDIJK BY 2240.2. z.l-

, AGENT Feb. 18, 1969 J. A. RIETDIJK DEVICE FOR PRODUCING COLD AND/ORFOR LIQUEFYING GASES Sheet Filed Dec. 2. 1965 INVENTOR. J0 HAN A-RIETDIJK AGEN Feb. 18, 1969 J. A. RIETDIJK 3,427,317

DEVICE FOR PRODUCING COLD AND/0R FOR LIQUEFYING GASES- Filed Dec. 2.1965 Sheet 5 of 5 INVENTOR. JOHAN A. RIETDIJK AGENT United States Patent6414856 US. Cl. 62-113 17 Claims Int. Cl. F25b 1/10, 41/00, 5/00ABSTRACT OF THE DISCLOSURE A gas refrigerator having a high pressuremedium supply and incorporating at least two devices for cooling andpressure reduction of said medium. One of the devices is an ejectorwhich additionally pumps up part of the medium at the lowest pressureand temperature to said ejector to mix with the cooled andpressure-reduced medium.

The invention relates to a device for producing cold and/or forliquefying gases. This device comprises at least one high-pressuremedium supply, which communicates with one or with a plurality ofseries-connected heat exchangers in which the high-pressure medium iscooled as far as below the inversion temperature associated with thepressure concerned. The device comprises furthermore at least one memberin which the high-pressure medium cooled in the heat exchanger issubjected to reduction in pressure, while there are furthermore providedone or more containers in which the medium of reduced pressure can bebrought into thermal contact with a place to be cooled or can bewithdrawn from the device in the liquid state. The device comprisesfurthermore a duct system for conducting away the medium of reducedpressure, if desired through one or more of said heat exchangers.

In known devices of the kind according to the invention, Joule-Kelvincocks are employed for attaining the desired reduction of pressure. Thehigh-pressure medium is choked therein to a considerably lower pressure.With correctly chosen pressure and temperature the choking processbrings about a decrease in temperature of the medium or a phasetransition of part of the medium or both phneomena. The medium ofreduced pressure can then be brought into thermal contact with an objectto be cooled or a medium to be cooled. In the event of a phasetransition part of the liquid obtained may, if desired, be conductedaway from the device. The low-pressure vapour produced is then conductedaway to the surroundings or back to a compressor which supplies thehigh-pressure medium. y

In order to attain very low temperatures, it is necessary to choke downto very low pressures. If, for example helium is' used as a medium, andif a temperature of 4.2 K. is wanted, it is necessary to choke down toabout 1 atomsphere; 3.6 K. requires choking to about 0.5 atmosphere.Still lower temperatures require choking to even lower pressures. Thismeans that in the case of a closed system the compressor must be verybulky, while the low-pressure side of the heat exchangers must have alow 3,427,817 Patented Feb. 18, 1969 flow resistance. Therefore, theknown devices are complicated bulky and expensive. In the case of anopen system, which means that the high-pressure medium is derived fromsome source whereas the medium of reduced pressure is conducted away tothe surroundings subsequent to heat exchange with the object to becooled, and if cold is to be supplied at temperatures associated with asubat-rnospheric pressure, the device cannot blow off automatically.Therefore, additional steps are required for conducting away the mediumof reduced pressure from the device.

A further disadvantage of the known devices consists in that in theJoule-Kelvin cocks, the energy of the high-pressure medium is uselesslydissipated, which means losses.

The invention has for its object to obviate said disadvantages and ischaracterized in that in operation at least one of said containers has apressure which is lower than the reduced pressure in another containerwhich the medium is conducted away from the device, while the member inwhich the pressure is reduced comprises at least one ejector to which atleast part of the cooledhigh-pressure medium can be supplied, thesuction side of said ejector being in connection with outlet of saidcontainer of lower pressure, whereas the outlet of the reduced pressurecontainer communicates with the duct system through which the medium ofreduced pressure can be conducted away from the device.

An ejector is herein understood to mean a member in which the potentialenergy of a high-pressure (primary) medium is converted wholly or partlyinto kinetic energy, which is utilized at least partly for raising thepressure of a further (secondary) medium.

According to the invention the energy of the high-pressure mediumsupplied to the ejector is utilized at least partly for applying apartial vacuum to the vapour from the lower-pressure container and forbringing it to the pressure prevailing in the duct system through whichthe medium of reduced pressure is conducted away from the device. Thecold can then be delivered at a pressure which is lower than the outletpressure of the reduced pressure container. In the event of an opensystem this involves the advantage that blowing-off is performedautomatically, while the cold is supplied at a pressure lower than theblowing-01f pressure.

If, according to a further aspect of the invention, there is provided acompressor, the outlet of which communicates with the high-pressuremedium supply and the inlet of which communicates with the outlet forthe medium of the reduced pressure container, the pressure ratio of thecompressor may be considerably lower than in known devices of the kindset forth.

The difference between the known devices and the device according to theinvention resides in that the pressure energy of the medium supplied tothe ejector is not uselessly dissipated and is employed for pumping upthe vapour from the lower-pressure container to the suction pressure ofthe compressor or to the pressure at which the medium leaves the device.In this way the resultant device has a higher efliciency and a much morefavourable pressure ratio in the heat exchanger and the compressor. Thedevice thus obtained is cheaper and has considerably smaller dimensions.

A further advantageous embodiment of the device according to theinvention is characterized in that there are provided one or moreparallel-connected ejectors, the inlet side(s) of which com-municateswith the high-pressure part of the heat exchanger(s) and the outletside(s) of which communicates with a collecting receptacle. The vapourspace of each receptacle communicates with the outlet duct system forthe reduced-pressure medium, and the device comprises a furthercontainer which communicates through a duct including a choke with thecollecting receptacle, preferably with the liquid part of saidcontainer, the vapour space of said further container communicating withthe suction side of said ejector(s). In this device the furthercontainer may have a lower pressure than the collecting receptacle, sothat the cold is delivered at a lower temperature. The vapour is drawnout of the further container by the ejector and raised to the presenceprevailing in the collecting receptacle.

A further advantageous embodiment of the device according to theinvention is characterized in that it comprises two or more ejectors,the inlet side of each of which communicates with the high-pressureportion of the heat exchanger, and the outlet side of each ejectorcommunicates with a reservoir. Said reservoirs have, in operation,progressively lower pressures and are connected in series with eachother through ducts including chokes, the higher-pressure sides of saidducts preferably opening out in the liquid spaces of the relevantcontainers. The container of the lowest pressure communicates through aduct including a choke with a further container in which a still lowerpressure prevails, while the vapour space of each container, with theexception of the vapour space of the container of the highest pressure,communicates with the suction side of an ejector, and the outlet side ofeach communicates with a container of higher pressure, while the vapourspace of the container of the highest pressure joins the outlet ductsystem for the medium of reduced pressure. This embodiment consequentlycomprises a plurality of containers of different pressures so that it ispossible to derive cold from this device at different temperatures.

In a further advantageous embodiment there are provided a number ofseries-connected ejectors. The inlet side of the first ejector joins thelast heat exchanger, whereas the last ejector joins by its outlet sidethe collecting receptacle. The vapour space of the receptaclecommunicates with the outlet duct system for the reducedpressure medium.There is furthermore provided one or more additional containerscommunicating with each other through appropriate ducts includingchokes, the first additional container communicating with the collectingreceptacle, whereas the vapour space of each of the additionalcontainers communicates with the suction side of one or more of theejectors. In this way a number of containers have gradually lowerpressures and hence also a gradually lower temperature. It is thuspossible to derive cold from this device at different temperatures. Itis furthermore possible to establish a thermal contact between, forexample, a medium in order of succession with the medium in the variouscontainers, so that said medium is cooled at different temperaturelevels.

In a further embodiment one or more chokes are connected in parallelwith the ejectors, so that part of the medium emanating from thehigh-pressure portion of the heat exchanger(s) passes through saidchokes and then into the collecting receptacle and/or one of the furthercontainers.

A further advantageous embodiment of the device according to theinvention is characterized in that it comprises only one container,which communicates through a choke with the high-pressure portion of theheatexchanger(s), the device comprising furthermore an ejector, theinlet side of which also joins the high-pressure portion of theheat-exchanger(s), whereas the outlet side of the ejector communicateswith the outlet duct system for the reduced-pressure medium, the suctionside of the ejector communicating with the vapour space of thecontainer. A lower pressure prevails in the container than the pressureat which the medium is conducted away.

In a further advantageous embodiment of the device according to theinvention each of the communicating ducts (between the suction side ofeach of the ejectors, and a vapour space of an additional container)includes one or more heat-exchangers in which the medium flowing to thesuction side of the ejectors exchanges heat with the higher-pressuremedium. The efiiciency of the device is thus improved.

A further advantageous embodiment of the device according to theinvention includes a control-member which governs one or more of thechokes in the ducts between the liquid spaces of the respectivecontainers in dependence upon the liquid level in said containers. Thecontrol-member may be formed by a float which determines the position ofthe choke concerned.

According to a further aspect one or more of the ejectors iscontrollable, so that the flow of high-pressure medium passing throughsaid ejector(s) can be controlled. The device can thus be adapted tovarying conditions.

A further advantageous embodiment of the device according to theinvention, which is particularly suitable for producing cold at very lowtemperatures, is characterized in that it comprises a machine forproducing cold at low temperatures, which comprises one or morecompression spaces filled with a working medium and one or moreexpansion spaces of variable volume, said spaces communicating with eachother and having, in operation, relatively different averagetemperatures, the communication between each of said spaces includingone or more regenerators, while the high-pressure medium flowing towardsthe ejector(s) or the choke(s) is in thermal contact with the workingmedium in the expansion space(s).

In a further advantageous embodiment the machine for producing cold atlow temperatures, if required, together with an additional compressionmember, serves at the same time as a compressor for the medium flowingto the ejector(s) or choke(s), said machine being provided with anoutlet valve and an inlet valve, said valves communicating with the heatexchanger(s) through which the medium flows 'to the ejector(s) or thechoke(s) and the duct system joining the collecting recipient.

It should be noted that for the construction, the control, etc., of thedevice according to the invention all techniques commonly used incompression refrigerators may be employed.

In this way an extremely advantageous construction of a device producingcold is obtained.

The invention will be explained more fully with reference to thedrawing.

FIGS. 1a and 1b show two known devices for producing cold indiagrammatic views.

FIGS. 2 to 7 show diagrammatically a number of embodiments of devicesfor producing cold, each comprising one or more ejectors.

FIG. 8 shows diagrammatically a device for producing cold, whichcomprises apart from an ejector a cold-gas refrigerator for cooling thecompressed working medium.

FIG. 9 shows diagrammatically a device for producing cold, whichcomprises an ejector and a cold-gas refrigerator serving as a compressorand as a cooling aggregate for the medium to be expanded.

FIG. 1a shows a known device for producing cold, comprising acompressor 1. The outlet 2 of the compressor communicates with thehigh-pressure portion 3 of a heat exchanger. The medium cooled in theheat-exchanger is choked in a choking cock 4, which joins a collectingreceptacle 5. To the recipient 5 a quantity of heat can be supplied, forexample by passing the medium to be cooled through a helix 6. Instead ofa medium passed through the helix, an object to be cooled may be broughtinto thermal contact with the container 5 and the liquid containedtherein. The vapour in the container 5 is passed through thelow-pressure portion 7, of the heat exchanger to the inlet 8 of thecompressor 1.

The temperature at which the cold is supplied (temperature of the liquidin the container 5) depends upon the pressure in said container. Thelower the pressure, the lower is the temperature. If, for example,helium is the Working medium, a pressure of about 1 atmosphere in thecontainer 5 will correspond to a temperature of 4.2" K. It is oftendesirable to attain lower temperatures. This may be achieved by choosinga lower pressure in the container 5. At a pressure of 0.5 atmosphere atemperature of 3.6 K. prevails, and so on. At these low pressures in thecontainer 5 the gas flowing through the portion 7 of the heat-exchangerwill have a particularly large volume, so that the heat-exchangers musthave a large passage in order to ensure low flow resistance. Since aclosed system is concerned here, the compressor must be very large owingto the high pressure ratio.

An improved known construction of the aforesaid device is shown in FIG.lb. The device comprises a compressor 1, the outlet 2 of whichcommunicates with the high-pressure portion 3 of a heat-exchanger. Themedium is chocked in the choking member 4. The choke medium is collectedin a receptacle 9, in which an average pressure prevails. The vapourspace of the receptacle 9 communicates through a portion 10 of theheatexchanger with the inlet 8 of the compressor 1. The receptacle 9communicates through a duct 11 including a choking member 12 with acontainer 5 having lower pressure. In this container there is arranged ahelix 6 to be cooled. The vapour space of container 5 communicatesthrough the portion 7 of the heat exchanger with the surroundings. Inthis device choking is performed stepwise, which is conducive to theefficiency. Since the duct 7 opens out in the atmosphere, the pressurein the container 5 cannot be lower than the atmospheric pressure. Thevapour formed in the container 5 is blown off and must be raised inpressure in some way or other. Particularly, if it is desired to producecold at gradually lower temperatures, this involves a very complicatedheat exchanger and a bulky compressor.

The devices according to the invention shown in the figures to bedescribed hereinafter obviate the disadvantages of the known devicesdescribed above, while all advantages thereof are maintained.

FIG. 2 shows a device which comprises a compressor 1. The outlet 2 ofthis compressor communicates with the high-pressure portion 3 of a heatexchanger. The portion 3 joins the supply side of an ejector 21. Theoutlet 22 of the ejector 21 is connected with a collecting receptacle23. The vapour space of the receptacle 23 communicates through theportion 7 of the heat exchanger with the inlet 8 of the compressor. Thecollecting receptacle 23 communicates through a duct 24 including achoke 25 with an additional container 26. The vapour space of thecontainer 26 communicates through a duct 27 including heat exchangers110 and 111 with the suction side 28 of the ejector 21. The container 26accommodates a helix 29, through which the medium to be cooled can beconducted. There is furthermore provided a control-member 30, whichcontrols the choke 25 in dependence upon the liquid level in thecontainers 23 and 26. If necessary, the ejector may be provided with acontrol-member 120. By varying the position of the member 120, thehigh-pressure medium flow passing through the ejectors can be adjusted.

This device operates as follows.

The compressor 1 compresses a medium, for example, helium to a pressure12 This high-pressure medium is cooled in the heat exchanger 3 and thensupplied to the ejector, in which it is subjected to a reduction ofpressure, while the potential energy is partly converted into kineticenergy, which is partly employed for obtaining the pressure of thehigh-pressure medium. The medium leaving the ejector with a pressure pis collected in a receptacle 23. The vapour at a pressure p can thenflow through a portion 7 of the heat-exchanger back to the compressor.The liquid obtained is choked in the choking member ,25 to a pressure 12which is associated with the temperature at which cold has to bedelivered. The vapour in the receptacle 26, having a pressure 12 isdrawn by the ejector 21 and brought to the pressure p of the collectingreceptacle 23. Before entering the ejector 21, the vapour of thecontainer 26 exchanges in heat exchangers and 111 heat with a medium ofhigher pressure. In the ejector 21 the energy of the high-pressuremedium (17 is partly used for applying a partial vacuum to the container26 and pumping up the vapour therein to a pressure p The pressure pprevailing in the vessel 26, and corresponding to the desired lowtemperature, may be considerably lower than the pressure p in thereceptacle 23. In this device the compressor is operative between thepressures p and 17 so that it may be structurally much more simple thanin the known devices, in which the compressors operate between thepressures p and 17 FIG. 3 shows a modification of the device of FIG. 2.

This device comprises three series-connected ejectors 31, 32 and 33. Thesupply side 34 of the ejector 31 communicates with the portion 3 of theheat exchanger. The outlets 35, 37, and 39 of the ejectors 31, 32 and 33respectively communicate with the inlet sides 36, 38 of the ejectors 32and 33 respectively and with the collecting receptacle 40. The devicecomprises three additional containers 41, 42 and 43, which communicatewith each other through ducts including choking members 44, 45 and 46respectively. The vapour spaces of the additional containers 41, 42 and43 communicate through ducts 49, 48, 47 respectively including heatexchangers 112, 113, 114 and 115, 116, 117 respectively with the suctionsides 50, 51 and 52 of the ejectors 33, 32 and 31 respectively. Thecontainer 43 includes a helix 29, through which a medium to be cooledcan be passed. If desired, the containers 40, 41 and 42 may be providedwith such helices, so that the device is capable of supplying cold atdifferent temperatures. If desired, a medium to be cooled may be broughtinto thermal contact with the medium in the containers 40, 41, 42 and43. The high-pressure medium from the compressor 1 is subjected in theejectors 31, 32 and 33 stepwise to a reduction in pressure. After theejectors the medium is collected in the container 40. The vapour canflow out of this container back to the compressor. The liquid from thecontainer 40 is also subjected stepwise to a reduction in pressure, sothat a progressively lower pressure prevails in the container 41, 42 and43. The low-pressure vapour from the containers 41, 42 and 43 is drawnby the ejectors 33, 32 and 31 respectively and brought to the pressureprevailing in the container 40. In this way an extremely simplestructure is obtained for a device which is capable of supplying cold atdiflerent temperatures. Although the drawing shows only three ejectorsand three additional containers, it will be obvious that this number maybe enlarged or diminished at will. Moreover, as is shown in FIG. 3a, anumber of series-connected ejectors may be connected by their suctionsides with one additional container.

Although, as shown in the drawing, the additional containers areconnected in a given order of succession, with the respective suctionsides of the ejectors, it will be obvious that this order may bechanged, if desired, while the device is nevertheless capable ofsupplying cold.

FIG. 4 shows diagrammatically a device for producing cold, whichcomprises three ejectors 121, 122 and 123. These ejectors communicate bytheir inlet sides 124, 125 and 126 respectively, with the high-pressureportion 3 of the heat-exchanger. The ejector 121 communicates by itsoutlet 127 with a container 128, in which a pressure p prevails. Theejector 122 communicates by its outlet 129 with the container 130 havinga pressure 11 The ejector 123 communicates by its outlet 131 with acontainer 132, in which a pressure p, prevails. The containers 128, 130and 132 communicate through ducts including choking cocks 133 and 134with each other and the container 132 communicates through a ductincluding a choking cock 135 with an additional container 136, in whicha pressure 1 prevails. The vapour spaces of the containers 136, 132 and130 communicate with the suction sides 137, 138 and 139 respectively ofthe ejectors 123, 122 and 121 respectively. The device comprisesfurthermore a number of heat-exchangers 140, 141, 142 and 143, in whichthe various flows of medium exchange heat. The vapour space of thecontainer 128 communicates with the low-pressure portion 7 of theheat-exchanger. In this device a number of containers is available, inwhich different pressures prevail, so that if desired the cold can bederived at different temperatures. The ejectors of this device receivethe primary medium at the same pressure p FIG. 5 shows a device forproducing cold, in which the compressed and cooled medium emanating fromthe high-pressure portion 3 of the heat-exchanger is split up in twoportions. A suitably chosen portion is supplied to an ejector 60 and theother portion to a choking member 61. The outlets of the ejector and thechoking member both open out in the container 62. The vapour space ofthis container 62 communicates with the inlet 8 of the compressor 1,while the container communicates furthermore through a choking member 63with an additional container 64. The container 64 accommodates aheat-exchange helix 29. The vapour space of container 64 communicateswith the suction side 65 of the ejector 60. This ejector draws thelow-pressure vapour out of the container 64 and raises it to thepressure prevailing in the container 62. A control-member providesconstant liquid levels in the containers 62 and 64. In this case thepressure ratio between inlet and outlet of the ejector 60 and thechoking member 61 is the same. However, the outlet of the choking cockmay be connected with the container 64 of lower pressure. Thisalternative is illustrated in the drawing by broken lines.

FIG. 6 shows a device for producing cold in a diagrammatic view, inwhich only one container 70 is provided, in which the desired lowpressure corresponding to the temperature of the cold supply prevails.The high-pressure portion 3 of the heat-exchanger communicates with achoking member 71, in which part of the compressed medium is choked. Thedevice comprises furthermore an ejector 72, the inlet side 73 of whichcommunicates with the high-pressure portion of the heat-exchanger. Thesuction side 74 of the ejector communicates with the vapour space of thecontainer 70-. The outlet 75 of the ejector communicates with theportion 7 of the heat-exchanger. From the foregoing the operation methodof this device will be obvious.

FIG. 7 shows a device corresponding with that of FIG. 6. The ejector 72is arranged here in the heat-exchanger 3, 7, which means that the vapourof the container 70 exchanges heat in the portion 7' with the mediumflowing towards the choking cock 71, after which it is supplied to thesuction side 74 of the ejector 72. The outlet 75 of the ejector 72communicates with a second portion 7 of the heat-exchanger. The ejector72 receives the primary medium from a place 76 of the portion 3 of theheat-exchanger.

FIG. 8 shows a device for producing cold at low temperatures, whichcomprises a cold-gas refrigerator 80 of the multi-space type. Thisrefrigerator comprises a compression piston 81, which is adapted to movein a cylinder 82. The cold-gas refrigerator comprises furthermore adisplacer piston, which consists of two portions 83 and 84 of differentdiameters. The compression piston 81 and the displacer piston aremovable with phase difference and they vary the volume of a compressionspace 85 and of the expansion spaces 86 and 87. The compression space 85and the expansion space 86 communicate with each other through a cooler88, a regenerator 89 and a first freezer 90. The expansion spaces 86 and87 communicate with each other through a regenerator 91 and a secondfreezer 92. In operation the first freezer has a temperature of about 80K. whereas the second freezer has a temperature of about 15 K.

A compressor 1 compresses a medium, for example, helium. The compressedmedium first passes through a portion 3 of a heat-exchanger. Then themedium exchanges heat in a heat-exchanger 95 with the first freezer 90.It then flows through a portion 3" of a heat-exchanger and exchangesheat in the heat-exchanger 96 with the second freezer 92 and finally itpasses through a further portion 3" of a heat-exchanger, after which thecooled medium is supplied to an ejector 21, the outlet of whichcommunicates with a collecting receptacle 23. The receptaclecommunicates through a duct 24 including a choking member 25, controlledby a float 97, with a container 26. The vapour space of the container 26communicates through the duct 27, including heat-exchangers, with thesuction side of the ejector 21. The vapour space of the container 23communicates through the heat-exchangers 7", 7" and 7 with the inlet 8of the compressor 1. In this way an extremely efficient device forproducing cold at low temperatures is obtained.

Finally, FIG. 9 shows a device for producing cold at low temperatures,in which the compressor 1 is replaced by a cold-gas refrigerator 100,having an outlet valve 101 and an inlet valve 102. The outlet valve 101is constructed so that it opens when the pressure in the refrigeratorattains a given value exceeding the minimum pressure. The refrigeratorthus operates as a compressor and it is proportioned so that itsupplies, in addition, a quantity of cold so that the medium emanatingfrom the refrigerator is at a lower temperature than the incomingmedium.

Although in the embodiments shown the device cools a medium or anobject, it is possible to withdraw a given quantity of liquid from oneof the containers. The liquid withdrawn from the device must of coursebe replenished in the form of a gas to the compressor.

The drawing shows the compressor diagrammatically as a one-stage member.It will be obvious that under certain conditions use will be made of amulti-stage compressor. It is furthermore possible to obtain thehighpressure medium from a different source and to blow off the mediumof reduced pressure.

As will be apparent from the foregoing the invention provides asurprisingly effective construction of a device for producing coldand/or for liquefying gases, in which a lower pressure ratio prevails inthe compression member than in the known devices. The energy of thecompressed medium is not dissipated uselessly, but it is used forraising the pressure of the vapour of a container, in which a lowerpressure prevails and in which the medium is brought into thermalcontact with a place to be cooled or is withdrawn in the liquid statefrom the device.

The device according to the invention is capable of producing cold atany desired temperature.

I claim:

1. A gas refrigerator [for use with a medium dischargeable at a firsthigh pressure from a source, comprising:

(a) a first heat exchanger for receiving and cooling the high pressuremedium to a first temperature below its inversion temperature and aboveits critical temperature;

(b) a first ejector having ('1) a first inlet for receiving from theheat exchanger at least some of the cooled medium in a gaseous state,which medium is expandable in the ejector to a second intermediatetempera- 9 ture and pressure below that in said heat exchanger, (2.) anoutlet through which expanded medium is dischargeable, and (3) a suctioninlet for pumping medium therein;

(c) a first container having an inlet for receiving said expandedmedium, and first and second outlets,

(d) a choke means through which medium (from the first containers firstoutlet) is further expandable to a third pressure below that of thesecond pressure, and

(e) a second container having an inlet for receiving the furtherexpanded medium, and an outlet through which medium in vapor state ispumped to the suction inlet of the ejector, medium in the second container providing cold for cooling a substance brought into thermalcontact therewith, and the second outlet of the first container being adischange means for gaseous medium therein.

2. A gas refrigerator as claimed in claim 1 further comprising means insaid ejector for adjustably controlling the fiow of high pressure mediumpassing through said ejector.

3. Apparatus as defined in claim 1 further comprising: (a) at least oneadditional container connected in series between said choke and secondcontainer for medium to flow progressively between them;

(b) at least one additional choke means connected after each additionalcontainer for expanding the medium entering said containers toprogressively lower pres sures and temperatures;

(c) at least one additional ejector connected in parallel with the firstejector, each additional ejector having (1) its first inlet incommunication with high pressure supply medium, (2) its outlet incommunication with one of said containers, and (3) its suction inlet incommunication with the outlet of a container discharging at a lowerpressure than the outlet of said ejector.

4. Apparatus as defined in claim 1 further comprising:

(a) at least one additional container connected in series between saidchoke and second container for medium to flow progressively betweenthem;

(b) at least one additional choke means connected after each additionalcontainer for expanding the medium entering said containers toprogressively lower pressures and temperatures;

(c) at least one additional ejector connected in series with the firstejector, the ejectors operable at progressively descending pressureswith the outlet of one ejector discharging into the inlet of the subse-,quent ejector, the containers (in ascending order of pressure) eachdischarging into a suction inlet of one of the ejectors (in descendingorder of pressure), the container at highest pressure discharging vaporto the high pressure medium source.

5. Apparatus as defined in claim 1 further comprising at least oneadditional ejector connected in series between said first ejector andsaid first container, and each ejector having its suction inlet incommunication with the outlet of the second container.

6. Apparatus as defined in claim 1 further comprising a choke meansconnected in parallel with the ejector and discharging into the firstcontainer.

7. Apparatus as defined in claim 1 wherein at least some of the mediumin each container is in liquid state and at progressively lowertemperature, for providing refrigeration at different temperatures.

8. Apparatus as defined in claim 7 further comprising a control memberresponsive to the liquid levels in said containers for governing thechoke between said containers.

9. Apparatus as defined in claim 1 further comprising an additional heatexchanger comprising first and second freezers of a Stirling cycle coldgas refrigerator through which the high pressure medium is flowed andprogressively cooled before entering said first heat exchanger.

10. Apparatus as defined in claim 1 wherein said choke is combinedwith-a float valve for automatically controlling the flow of mediumbetween said containers.

11. Apparatus as defined in claim 1 in combination with a cold gasrefrigerator which is said source of cooled high pressure medium.

. 12. Apparatus as defined in claim 1 wherein cold from said mediumdischarged from the first container is transferred to medium flowing tosaid ejector in counterflow heat exchange. 1

13. Apparatus as defined in claim 1 further comprising a second heatexchanger wherein cold from the medium discharged from the secondcontainer is transferred to medium flowing to said choke.

14. A gas refrigerator for use with a high pressure medium dischargeablefrom a source which also includes an inlet, comprising:

(a) a heat exchanger for receiving and cooling the high pressure mediumto a first temperature below its inversion temperature and above itscritical temperature;

(b) a choke means through which medium, (from the heat exchanger) flowsand is expanded to a pressure below that of the source;

(c) a container for receiving medium discharged from the choke and forproviding cold for cooling an article brought into thermal contacttherewith, and

(d) an ejector having its inlet in communication with high pressuremedium from the heat exchanger, its suction inlet in communication withand for pumping medium from an outlet of the container, and its outletin communication with the heat exchanger which is then communicated toan inlet of the medium source.

15. Apparatus as defined in claim 14 wherein the medium dischargeablefrom the ejector provides-cold for said heat exchanger and the mediumflowable from the container to the ejectors suction inlet also providescold for the heat exchanger.

16. A refrigerating method using a fluid medium having initial highpressure and temperature comprising the steps:

(a) cooling the medium in its gaseous state to a first temperature belowits inversion temperature and above its critical temperature;

(b) expanding the cooled medium in an ejector to a second temperatureand pressure below that in its initial state;

(0) collecting the cooled medium in a first container with vaportherefrom being dischargeable;

((1) further expanding at least some of the collected medium to a thirdtemperature and pressure below that of the medium in the firstcontainer;

(e) collecting the further expanded medium in a second container and (f)pumping vapor of said further expanded medium to a suction inlet of saidejector by using the kinetic energy developed during said expansion inthe ejector, whereby cold is provided in said first and secondcontainers for refrigerating at progressively lower temperatures.

17. A refrigerating method using a fluid medium having initial highpressure and temperature, comprising the steps:

' (a) cooling the medium in its gaseous state to a first temperaturebelow its inversion temperature and above its critical temperature;

(b) expanding some of the cooled medium in an ejector to a secondtemperature and pressure below that in its initial state;

(c) expanding the remainder of the cooled medium through a choke to athird temperature and pressure below that in its initial state;

1 1 1 2 (d) collecting in a container the medium expanded in ReferencesCited the choke, some of the collected medium being in a UNITED STATESPATENTS liquefied state for refrigerating matter brought into 2,014,7019 1 5 seligmann 62 500 XR thermal contact therewith, the remainder ofthe col- 2,146,797 2/1939 Dasher 62500 XR lected medium being vapor, 52,513,361 7/ 1950 Rausch 62-50O XR (e) drawing at least some of saidvapor into the suctlon 1nlet of the e ector by the k1net1c energydeveloped during said expansion in said ejector, and MEYER PERLIN,Primary Examiner. (f) discharging the expanded medium from the ejector10 u CL to a heat exchanger for said cooling step (a). 62117, 191, 500

